Rigid magnetic data disk storage devices achieve high volumetric storage densities by utilizing the maximum number of data surfaces and high areal storage densities on the disk surfaces. The height of the disk stack is limited by the form factor or industry standard dimensions that disk drives must adhere to in order to achieve commercial acceptance. The drive can maximize the number of data surfaces by utilizing the total form factor height for the disk stack. Spacing between disks can be reduced to the minimum spacing required for the functioning of the transducer head, its suspension and the actuator arm to which the head-suspension assembly is mounted. A further step is to reduce the thickness of the data disk.
When these parameters have been optimized to the current state of the art, the ability of the disk clamping within the disk stack to maintain the disks flat, parallel and free of deformation becomes critical. For a given clamping force on a disk stack, concentrated loads will tend to cause more severe disk deformation than distributed loads. One typical distortion mode is coning (or cupping) of the disks. The distortion problem has been observed on industry standard thickness disks and is more severe on reduced thickness thin disks. The coning of the disks is detrimental because it affects the fly height of the heads. With the higher bit densities and lower fly heights required by high density thin disks, the flatness of the disks in the disk pack assembly becomes increasingly important.